1. Field of the Invention
The subject invention relates generally to antennas and, more particularly, to a method for locating failed elements in an active antenna array.
2. Description of Related Art
An assembled active antenna array is complex, typically including thousands of modules, sometimes also referred to as "elements." These modules typically contain a receive path and a transmit path. The receive path typically includes a low noise amplifier outputting to a receive phase shifter whose phase shifted output is combined with that of the receive phase shifters of other modules and supplied to a main receiver and filter. The module's transmit path includes a transmit phase shifter which phase shifts the transmit signal and supplies the phase shifted transmit signal to an output power amplifier.
Each of the modules of an active antenna array thus includes a number of elements and may fail in a variety of ways. It is costly and time-consuming to remove an active array from an aircraft or other carrier in order to replace defective modules. Thus, if some modules do fail after installation, it becomes important to partially compensate for performance degradation without physical replacement.
Studies have shown that the impact of a failed module can be minimized by turning it off. This, of course, implies that such failed modules must be detectable. Evaluating a failed module is complicated by the fact that leakage power from other modules in the array will likely swamp the power of a single active module. Accordingly, there is a need in the art for a method of locating a failed module or element in an active antenna array.